Halloween isn't for another week, but we've already seen some awesome costumes from some of our favorite celebs!

Kelly Osbourne looked like a spot-on Dame Edna at MAC and Rick Baker’s Monster Mash earlier this week -- but it's her fiance Matthew Mosshart who really wins Best Costume for this couple.

Check out the gallery above to see his HILARIOUS "Blossom" costume. Mayim Bialik would be proud!

Other stars at that bash included appearances from a skeletal Jason Priestley (right), Lucas Till and a devilish Slash.

Wonder Woman appears to be a popular costume this year, as Jenny McCarthy, Joanna Krupa and Melissa Gorga have all been seen wearing the sexy number. Who wore it best? Tell us below!

And, in case you missed it, see Neil Patrick Harris' adorable family photo -- plus shots of Martha Stewart, "Modern Family" star Rico Rodriguez and many more in the gallery above!

Keep checking back all weekend long, as a number of celebrity costume parties will be held over the next few days.

What are you dressing as this year?